A method for joining the ends of rope (strands, wire, cable, etc.) is necessary in mechanical operations, including lifting, towing, or the like. The rope ends being joined can be either of different pieces of rope (in order to make a longer length rope), or the ends can be of the same piece of rope (to form a continuous or "endless" loop).
An example of this latter use is the well-known commercial "rope-tow" system used to pull skiers up hills. The ends of the rope are usually joined by a "splice," (defined as a joint accomplished by "weaving" the ends of the rope together).
The "splice" is an ideal method for this commercial application, where a relatively large rope diameter (1/2" to 3/4" approx.) is used in a permanent and high cost installation, where there is little likelyhood of having to re-splice the rope. The "splice" method has the advantage of being practically the same diameter and strength as the parent rope. However, the "splice" method has the disadvantage of being difficult to make, and does not lend itself to being done by an inexperienced person, and the method is very time consuming.
In towing operations using smaller diameter rope (for lighter loads), the splice is not too desirable to use. These applications might include use for:
1. Cross-country skiing, where rope sizes might be 1/8" to 1/4" diameter (approx.). Here, light weight rope is desirable, as the rope might be carried to the tow site by a skier; the rope might be left inattended for some periods of time, (making it desirable to use a rope of low dollar value), or the rope may be moved to another slope, requiring a probable change in overall length.
2. Marginal snow areas, which might not justify the high cost of a permanent type installation.
3. Beginner's practice tow for low cost and "backyard" applications, etc.
Some other methods of joining ropes (strands, wire, cable, etc.), besides the splice, include:
1. Use of an auxiliary piece, (tubing, clamp, or the like). However, it is difficult to find a product which gives a joint which has the strength approaching the strength of the rope, while still being sufficiently flexible to bend when going around the support and drive pulleys, and at the same time be relatively smooth, and without any objectionable protrusions, which increase chances of entanglement, etc.
2. Use of a bare knot. This method has the disadvantage of having an abrupt change in diameter, which increases chances of entanglement, etc.
3. Use of a knot and a knot cover. This cover can smooth out the abrupt change in the diameter of the rope section caused by the knot. The cover can have the shape of a conical wedge or ramp. The cover can be either a "double ended" wedge (for movement in either direction) or a "single ended" wedge (for movement in one direction only). More details are provided below.
This method of the knot cover relates to the present invention, and wherein an improvement to the generally available method of using a bare (uncovered knot, said improvement comprising the addition of a joint cover means to accomplish the desired result.
Optional methods available for forming a joint cover means to smooth out abrupt changes in diameter include:
A. Use of sleeving, in forms as follows:
1. Uniform diameter, with methods to form the necessary wedge shape. (This method relates to the present invention.) PA1 2. Non-uniform diameter. Problems: high cost and difficult to obtain. PA1 Problems: (same as B.) PA1 Problems: It is difficult to obtain a suitable castable resin which would be flexible enough for bending, and still have a wear resistant and "low-friction" surface, and it would probably require time for hardening. PA1 A. long life expectancy PA1 B. resisting stresses caused by bending, as the joint area travels around the rope support pulleys, drive pulleys, or system components (as ski-tow devices, etc.).
B. Wrap knot area with "tape" type material to form a cover. Problems: probably low flexibility and low endurance.
C. Wrap knot area with "thread" type material to form a cover.
D. Cover knot area with a "castable resin" type material.
4. Use of a method to form the ends of the strands into "hook" shapes which are then interlocked, and the joint is then covered in some method to resist separation. It can be seen that the strength of this joint is dependent on the stiffness of the hook section to resist straightening.
This method relates to the "Prior Arts Patent" listed below. It can be seen that the present invention differs from the referenced "Prior Arts Patent" in factors including:
A. Difference in the flexibility of the strands being joined. As a rope of sufficient flexibility to be joined with a knot, would be too flexible to retain a hook shape necessary for a strong joint. Conversely, a strand of sufficient stiffness to retain a hook shape, would be too stiff to joined with a knot.
B. The present invention uses the sleeving to form a joint cover to smooth out abrupt changes in diameter (caused by the joint), for the purpose of reducing entanglement tendencies, etc., as with adjacent segments of the rope or mating parts of the system.
C. The present invention does not necessarily use the sleeving to prevent separation of the joint, which separation appears to be the purpose in the Prior Art reference.
D. The present invention uses heat shrinking only in selected areas of the cover, leaving part of the tubing unshrunk, (to provide increased flex life).